One by one, prostitutes in spokane, washington are being hunted down and discarded in remote wooded areas by a vicious serial killer. On each victim’s head, police find his macabre calling card – a plastic bag emblazoned with an ironic smiley face. Investigators soon realize they are dealing with the worst type of serial killer – an average joe with no criminal background and with the extraordinary ability to blend in with the community. With few clues to work with – and as the death toll continues to rise – investigators turn to ballistics experts, space age fingerprinting technology, and to a forensic botanist who believes he can solve the crime by reading plants and trees.